Laboratory of Stem Cell Biology, Department of Biotechnology, College of Veterinary Medicine, Seoul National University, Seoul, 151-742, Republic of Korea.
Cell Mol Life Sci. 2013 Feb;70(4):711-28. doi: 10.1007/s00018-012-1157-4. Epub 2012 Sep 30.
Argonaute 2 (Ago2) is a pivotal regulator of cell fate in adult stem cells. Its expression is significantly downregulated in late passages of cells, concomitant with a prominent increase in Ago2 cytosolic localization in single cells. Nuclear localization of Ago2 is crucial for the survival, proliferation, and differentiation of hATSCs (human adipose tissue-derived stem cells), mediated by the specific binding of the regulatory regions of functional genes, which positively or negatively altered gene expression. Ago2 targets genes that control stemness, reactive oxygen species scavenging, and microRNA expression, all of which are crucial for hATSC survival and self-renewal. Ago2 promotes cell proliferation and self-renewal by activating the expression of octamer-binding transcription factor 4 (Oct4). We confirmed the direct regulation of Oct4 activity by Ago2, as indicated by the results of the ChIP analysis. Methyl-CpG-binding protein 6 (MBD6) was detected as an Oct4 regulatory gene. As predicted, knockdown of MBD6 expression attenuated cell proliferation and eventually induced cell death. We hypothesized that MBD6 functions downstream of Oct4 in the regulation of stemness-related genes, cell proliferation, self-renewal activity, and survival. MBD6 also promoted cell transdifferentiation into neural and endodermal β-cells while significantly attenuating differentiation into the mesodermal lineage. We demonstrate that MBD6 is regulated by Ago2 via an interaction with Oct4, which alters self-renewal and gene expression in hATSCs. MBD6 was promoted cell proliferation through a novel set of signal mediators that may influence differentiation by repressing MBD2 and MBD3, which are possibly recruited by germ cell nuclear factor (GCNF).
Argonaute 2 (Ago2) 是成体干细胞命运的关键调节因子。其表达在细胞后期明显下调，同时单个细胞中 Ago2 胞质定位显著增加。Ago2 的核定位对于 hATSCs（人脂肪组织来源的干细胞）的存活、增殖和分化至关重要，这是通过功能基因的调节区域的特异性结合介导的，这些区域正向或负向改变基因表达。Ago2 通过激活八聚体结合转录因子 4（Oct4）的表达来靶向控制干细胞特性、活性氧物质清除和 microRNA 表达的基因，所有这些对 hATSC 的存活和自我更新都至关重要。Ago2 通过激活 Oct4 的表达来促进细胞增殖和自我更新。我们通过 ChIP 分析的结果证实了 Ago2 对 Oct4 活性的直接调节。甲基化 CpG 结合蛋白 6（MBD6）被检测为 Oct4 调节基因。正如预测的那样，敲低 MBD6 的表达减弱了细胞增殖，最终诱导了细胞死亡。我们假设 MBD6 在调节与干细胞特性相关的基因、细胞增殖、自我更新活性和存活方面在 Oct4 下游发挥作用。MBD6 还促进细胞向神经和内胚层 β 细胞的转分化，同时显著减弱向中胚层谱系的分化。我们证明 MBD6 通过与 Oct4 的相互作用受 Ago2 调节，这改变了 hATSCs 中的自我更新和基因表达。MBD6 通过一组新的信号介质促进细胞增殖，通过抑制可能由生殖细胞核因子（GCNF）募集的 MBD2 和 MBD3，可能影响分化。
